block: move dma_pad handling from blk_rq_map_sg into the callers

There are only two callers of blk_rq_map_sg/__blk_rq_map_sg that set
the dma_pad value in the queue.  Move the handling into those callers
instead of burdening the common code, and move the ->extra_len field
from struct request to struct scsi_cmnd.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -1638,7 +1638,6 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
 	}
 	rq->nr_phys_segments = rq_src->nr_phys_segments;
 	rq->ioprio = rq_src->ioprio;
-	rq->extra_len = rq_src->extra_len;
 
 	return 0;
 

block/blk-merge.c

@@ -531,14 +531,6 @@ int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
 	else if (rq->bio)
 		nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);
 
-	if (blk_rq_bytes(rq) && (blk_rq_bytes(rq) & q->dma_pad_mask)) {
-		unsigned int pad_len =
-			(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
-
-		(*last_sg)->length += pad_len;
-		rq->extra_len += pad_len;
-	}
-
 	if (*last_sg)
 		sg_mark_end(*last_sg);
 

block/blk-mq.c

@@ -318,7 +318,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 	rq->nr_integrity_segments = 0;
 #endif
 	/* tag was already set */
-	rq->extra_len = 0;
 	WRITE_ONCE(rq->deadline, 0);
 
 	rq->timeout = 0;

drivers/ata/libata-scsi.c

@@ -649,7 +649,7 @@ static void ata_qc_set_pc_nbytes(struct ata_queued_cmd *qc)
 {
 	struct scsi_cmnd *scmd = qc->scsicmd;
 
-	qc->extrabytes = scmd->request->extra_len;
+	qc->extrabytes = scmd->extra_len;
 	qc->nbytes = scsi_bufflen(scmd) + qc->extrabytes;
 }
 

drivers/ide/ide-io.c

@@ -233,10 +233,13 @@ static ide_startstop_t do_special(ide_drive_t *drive)
 void ide_map_sg(ide_drive_t *drive, struct ide_cmd *cmd)
 {
 	ide_hwif_t *hwif = drive->hwif;
-	struct scatterlist *sg = hwif->sg_table;
+	struct scatterlist *sg = hwif->sg_table, *last_sg = NULL;
 	struct request *rq = cmd->rq;
 
-	cmd->sg_nents = blk_rq_map_sg(drive->queue, rq, sg);
+	cmd->sg_nents = __blk_rq_map_sg(drive->queue, rq, sg, &last_sg);
+	if (blk_rq_bytes(rq) && (blk_rq_bytes(rq) & rq->q->dma_pad_mask))
+		last_sg->length +=
+			(rq->q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
 }
 EXPORT_SYMBOL_GPL(ide_map_sg);
 

drivers/scsi/scsi_lib.c

@@ -1030,13 +1030,21 @@ blk_status_t scsi_init_io(struct scsi_cmnd *cmd)
 	 */
 	count = __blk_rq_map_sg(rq->q, rq, cmd->sdb.table.sgl, &last_sg);
 
+	if (blk_rq_bytes(rq) & rq->q->dma_pad_mask) {
+		unsigned int pad_len =
+			(rq->q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
+
+		last_sg->length += pad_len;
+		cmd->extra_len += pad_len;
+	}
+
 	if (need_drain) {
 		sg_unmark_end(last_sg);
 		last_sg = sg_next(last_sg);
 		sg_set_buf(last_sg, sdev->dma_drain_buf, sdev->dma_drain_len);
 		sg_mark_end(last_sg);
 
-		rq->extra_len += sdev->dma_drain_len;
+		cmd->extra_len += sdev->dma_drain_len;
 		count++;
 	}
 

include/linux/blkdev.h

@@ -224,8 +224,6 @@ struct request {
 	unsigned short write_hint;
 	unsigned short ioprio;
 
-	unsigned int extra_len;	/* length of alignment and padding */
-
 	enum mq_rq_state state;
 	refcount_t ref;
 

include/scsi/scsi_cmnd.h

@@ -142,6 +142,7 @@ struct scsi_cmnd {
 	unsigned long state;	/* Command completion state */
 
 	unsigned char tag;	/* SCSI-II queued command tag */
+	unsigned int extra_len;	/* length of alignment and padding */
 };
 
 /*